There are vehicles such as automobiles having a device such as a car navigator or car audio equipment mounted thereon as a vehicle-mounted device of a so-called genuine spec authorized by the car maker. There are vehicles increasing in number, having a remote controller attached to a steering wheel to make a remote control of a genuine vehicle-mounted device. The steering-wheel-mounted remote controller (referred herein to as a steering remote control) is set up for adaptation to control a genuine vehicle-mounted device.
The genuine vehicle-mounted device may be replaced with another vehicle-mountable device generally available in the market. The steering remote control outputs preset signals (with voltage values) commensurate with the genuine vehicle-mounted device. The voltage values may be different between car makers or car types. Therefore, when connected to a commercially available vehicle-mountable device, the steering remote control is unable to work to operate the commercially available vehicle-mountable device as necessary.
To address this point, an adapter is proposed (Japanese Patent Application Laid-Open Publication No. 2007-320360 and No. 2007-230290) which inputs a signal from a steering remote control, converts it into a signal that a vehicle-mounted device can accommodate, and supplies the converted signal to the vehicle-mounted device.